If a team reflects its maker then it is no surprise to find Wigan flourishing as the season enters its defining phase. The first FA Cup semi-final in the club's history awaits at Wembley on Saturday , but it is the all too familiar relegation grind against wealthier opposition that captivates Roberto Martínez. "It would be my greatest achievement," is his take on preserving Wigan's Premier League status. Loosening Queens Park Rangers' hold on Sunday would reinforce that boast.

Martínez's team have provided one of the few constants of the spring with their annual reaction to the threat of relegation. Five wins in six games have lifted Wigan to 17th in the table and secured that semi-final against Millwall at Wembley, where the chairman Dave Whelan will lead out the team 53 years after breaking his leg in an FA Cup final. Martínez refers to the semi-final as "the reward" or "the celebration" for Whelan and his club. But the manager himself derives as much pleasure from the first trip to London and Loftus Road.

"I enjoy this time because I really enjoy Wigan Athletic having the big-club mentality when it comes to the final third of the season," the 39-year-old states. "Until then, we're allowed to lose, if that makes sense."

He explains: "As a football club, because we are enjoying an incredible story and being at this level is an achievement, there doesn't seem to be a real need to win at the weekend. Other football clubs have expectations and they've got the need of winning games. Now when we get into the final third, we all know that every game counts and the whole football club develops that big-team mentality. Now we are in April, we are involved in two major competitions, and I really enjoy the day-to-day expectation and need of winning games."

Martínez reads nothing into the seven-point advantage that Wigan enjoy over QPR, having played one game fewer than Harry Redknapp's side. "We all know this Queens Park Rangers team, if the season started now, would finish top 10," he claims. The Wigan manager does, however, find substance in the public outburst from Christopher Samba following his calamitous performance in QPR's defeat at Fulham on Monday.

"When you have got something to lose as a player, you can be affected and your performance can be affected," he says. "I don't think at Wigan Athletic that we have anything to lose. It is the opposite. We have eight games with something to win: our Premier League status. That, to us, is like winning a trophy. We have a real opportunity to win our title and that doesn't bring fear."

The £12.5m transfer fee and reported £100,000 weekly wage that QPR committed to Samba in January was bloated even by Premier League standards. To Wigan, who more than covered last summer's expenditure with the sale of Victor Moses to Chelsea for £9m, it demonstrates the achievement in remaining at the top level for eight successive seasons, a feat that is often overlooked.

Martínez reveals: "When I arrived the chairman was always putting money in at the end of the season and our target was to make the football club self-sufficient. What I'm very proud of is that we have made a profit this season. It's very significant at this level and we've been carrying on developing our youngsters.

"A wage of £100,000-a-week is what we would pay for three or four players. I have a budget. It is up to me to decide whether we have 12 or 13 players with a number of them earning huge wages, or whether we want a more balanced squad in terms of numbers and quality. Paying someone £100,000-a-week isn't practical here. We don't want to be relying on one or two players because we believe that you succeed as a squad. Other clubs might see it in a different way. They may be struggling a little bit when the January window opens and they are forced to pay over the odds to improve their chances. That isn't our strategy."

The manager believes this season's relegation contest has been "the hardest of the lot", as usually one or two teams have been cut adrift by now but "this year it is a really open fight". Out-manoeuvring Everton in the FA Cup quarter-final rekindled talk of a summer move for Martínez, while the impressive James McCarthy continues to attract covetous glances. "It would be dangerous for me to look into that now," the manager says of his own future. "All we are looking at is the next seven weeks. For me they are the most intense seven weeks that Wigan Athletic has ever had."

As for McCarthy, he adds: "I hope we'll struggle to hang on to him. The way he is going, James McCarthy will eventually play for a club that will play to win the title or the Champions League. For me, it's too early for him to go anywhere but eventually he'll go to one of the top clubs and it'll probably be for the record fee we've received."

That can wait, as must Wembley, where Martínez will face the manager for whom he served as captain at Swansea, Millwall's Kenny Jackett. "Wembley is a celebration for Wigan Athletic but we won't sacrifice the Cup for survival," he insists. "The priority is staying in this league but we have had to make sacrifices like that at this club for far too long."